1 bup: It backs things up
2 =======================
4 bup is a program that backs things up. It's short for "backup." Can you
5 believe that nobody else has named an open source program "bup" after all
8 Despite its unassuming name, bup is pretty cool. To give you an idea of
9 just how cool it is, I wrote you this poem:
12 What rhymes with awesome?
14 But that's irrelevant.
16 Hmm. Did that help? Maybe prose is more useful after all.
19 Reasons bup is awesome
20 ----------------------
22 bup has a few advantages over other backup software:
24 - It uses a rolling checksum algorithm (similar to rsync) to split large
25 files into chunks. The most useful result of this is you can backup huge
26 virtual machine (VM) disk images, databases, and XML files incrementally,
27 even though they're typically all in one huge file, and not use tons of
28 disk space for multiple versions.
30 - It uses the packfile format from git (the open source version control
31 system), so you can access the stored data even if you don't like bup's
34 - Unlike git, it writes packfiles *directly* (instead of having a separate
35 garbage collection / repacking stage) so it's fast even with gratuitously
36 huge amounts of data. bup's improved index formats also allow you to
37 track far more filenames than git (millions) and keep track of far more
38 objects (hundreds or thousands of gigabytes).
40 - Data is "automagically" shared between incremental backups without having
41 to know which backup is based on which other one - even if the backups
42 are made from two different computers that don't even know about each
43 other. You just tell bup to back stuff up, and it saves only the minimum
44 amount of data needed.
46 - You can back up directly to a remote bup server, without needing tons of
47 temporary disk space on the computer being backed up. And if your backup
48 is interrupted halfway through, the next run will pick up where you left
49 off. And it's easy to set up a bup server: just install bup on any
50 machine where you have ssh access.
52 - Bup can use "par2" redundancy to recover corrupted backups even if your
53 disk has undetected bad sectors.
55 - Even when a backup is incremental, you don't have to worry about
56 restoring the full backup, then each of the incrementals in turn; an
57 incremental backup *acts* as if it's a full backup, it just takes less
60 - You can mount your bup repository as a FUSE filesystem and access the
61 content that way, and even export it over Samba.
63 - It's written in python (with some C parts to make it faster) so it's easy
64 for you to extend and maintain.
67 Reasons you might want to avoid bup
68 -----------------------------------
70 - This is a very early version. Therefore it will most probably not work
71 for you, but we don't know why. It is also missing some
72 probably-critical features.
74 - It requires python >= 2.6, a C compiler, and an installed git
75 version >= 1.5.3.1. It also requires par2 if you want fsck to be
76 able to generate the information needed to recover from some types
79 - It currently only works on Linux, FreeBSD, NetBSD, OS X >= 10.4,
80 Solaris, or Windows (with Cygwin, and maybe with WSL). Patches to
81 support other platforms are welcome.
83 - Any items in "Things that are stupid" below.
86 Notable changes introduced by a release
87 =======================================
89 - <a href="note/0.29.1-from-0.29.md">Changes in 0.29.1 as compared to 0.29</a>
90 - <a href="note/0.29-from-0.28.1.md">Changes in 0.29 as compared to 0.28.1</a>
91 - <a href="note/0.28.1-from-0.28.md">Changes in 0.28.1 as compared to 0.28</a>
92 - <a href="note/0.28-from-0.27.1.md">Changes in 0.28 as compared to 0.27.1</a>
93 - <a href="note/0.27.1-from-0.27.md">Changes in 0.27.1 as compared to 0.27</a>
102 - Check out the bup source code using git:
104 git clone https://github.com/bup/bup
106 - Install the required python libraries (including the development
109 On very recent Debian/Ubuntu versions, this may be sufficient (run
112 apt-get build-dep bup
114 Otherwise try this (substitute python2.6-dev if you have an older
117 apt-get install python2.7-dev python-fuse
118 apt-get install python-pyxattr python-pylibacl
119 apt-get install linux-libc-dev
120 apt-get install acl attr
121 apt-get install python-tornado # optional
123 On CentOS (for CentOS 6, at least), this should be sufficient (run
126 yum groupinstall "Development Tools"
127 yum install python python-devel
128 yum install fuse-python pyxattr pylibacl
129 yum install perl-Time-HiRes
131 In addition to the default CentOS repositories, you may need to add
132 RPMForge (for fuse-python) and EPEL (for pyxattr and pylibacl).
134 On Cygwin, install python, make, rsync, and gcc4.
136 If you would like to use the optional bup web server on systems
137 without a tornado package, you may want to try this:
141 - Build the python module and symlinks:
149 The tests should pass. If they don't pass for you, stop here and
150 send an email to bup-list@googlegroups.com. Though if there are
151 symbolic links along the current working directory path, the tests
152 may fail. Running something like this before "make test" should
153 sidestep the problem:
157 - You can install bup via "make install", and override the default
158 destination with DESTDIR and PREFIX.
160 Files are normally installed to "$DESTDIR/$PREFIX" where DESTDIR is
161 empty by default, and PREFIX is set to /usr/local. So if you wanted to
162 install bup to /opt/bup, you might do something like this:
164 make install DESTDIR=/opt/bup PREFIX=''
166 - The Python executable that bup will use is chosen by ./configure,
167 which will search for a reasonable version unless PYTHON is set in
168 the environment, in which case, bup will use that path. You can
169 see which Python executable was chosen by looking at the
170 configure output, or examining cmd/python-cmd.sh, and you can
171 change the selection by re-running ./configure.
176 Binary packages of bup are known to be built for the following OSes:
179 http://packages.debian.org/search?searchon=names&keywords=bup
181 http://packages.ubuntu.com/search?searchon=names&keywords=bup
182 - pkgsrc (NetBSD, Dragonfly, and others)
183 http://pkgsrc.se/sysutils/bup
184 http://cvsweb.netbsd.org/bsdweb.cgi/pkgsrc/sysutils/bup/
186 https://www.archlinux.org/packages/?sort=&q=bup
188 https://apps.fedoraproject.org/packages/bup
194 - Get help for any bup command:
203 - Initialize the default BUP_DIR (~/.bup):
207 - Make a local backup (-v or -vv will increase the verbosity):
210 bup save -n local-etc /etc
212 - Restore a local backup to ./dest:
214 bup restore -C ./dest local-etc/latest/etc
217 - Look at how much disk space your backup took:
221 - Make another backup (which should be mostly identical to the last one;
222 notice that you don't have to *specify* that this backup is incremental,
223 it just saves space automatically):
226 bup save -n local-etc /etc
228 - Look how little extra space your second backup used (on top of the first):
232 - Get a list of your previous backups:
236 - Restore your first backup again:
238 bup restore -C ./dest-2 local-etc/2013-11-23-11195/etc
240 - Make a backup to a remote server which must already have the 'bup' command
241 somewhere in its PATH (see /etc/profile, etc/environment, ~/.profile, or
242 ~/.bashrc), and be accessible via ssh.
243 Make sure to replace SERVERNAME with the actual hostname of your server:
245 bup init -r SERVERNAME:path/to/remote-bup-dir
247 bup save -r SERVERNAME:path/to/remote-bup-dir -n local-etc /etc
249 - Make a remote backup to ~/.bup on SERVER:
252 bup save -r SERVER: -n local-etc /etc
254 - See what saves are available in ~/.bup on SERVER:
258 - Restore the remote backup to ./dest:
260 bup restore -r SERVER: -C ./dest local-etc/latest/etc
263 - Defend your backups from death rays (OK fine, more likely from the
264 occasional bad disk block). This writes parity information
265 (currently via par2) for all of the existing data so that bup may
266 be able to recover from some amount of repository corruption:
270 - Use split/join instead of index/save/restore. Try making a local
273 tar -cvf - /etc | bup split -n local-etc -vv
275 - Try restoring the tarball:
277 bup join local-etc | tar -tf -
279 - Look at how much disk space your backup took:
283 - Make another tar backup:
285 tar -cvf - /etc | bup split -n local-etc -vv
287 - Look at how little extra space your second backup used on top of
292 - Restore the first tar backup again (the ~1 is git notation for "one
293 older than the most recent"):
295 bup join local-etc~1 | tar -tf -
297 - Get a list of your previous split-based backups:
299 GIT_DIR=~/.bup git log local-etc
301 - Save a tar archive to a remote server (without tar -z to facilitate
304 tar -cvf - /etc | bup split -r SERVERNAME: -n local-etc -vv
306 - Restore the archive:
308 bup join -r SERVERNAME: local-etc | tar -tf -
310 That's all there is to it!
316 - FreeBSD's default 'make' command doesn't like bup's Makefile. In order to
317 compile the code, run tests and install bup, you need to install GNU Make
318 from the port named 'gmake' and use its executable instead in the commands
319 seen above. (i.e. 'gmake test' runs bup's test suite)
321 - Python's development headers are automatically installed with the 'python'
322 port so there's no need to install them separately.
324 - To use the 'bup fuse' command, you need to install the fuse kernel module
325 from the 'fusefs-kmod' port in the 'sysutils' section and the libraries from
326 the port named 'py-fusefs' in the 'devel' section.
328 - The 'par2' command can be found in the port named 'par2cmdline'.
330 - In order to compile the documentation, you need pandoc which can be found in
331 the port named 'hs-pandoc' in the 'textproc' section.
334 Notes on NetBSD/pkgsrc
335 ----------------------
337 - See pkgsrc/sysutils/bup, which should be the most recent stable
338 release and includes man pages. It also has a reasonable set of
339 dependencies (git, par2, py-fuse-bindings).
341 - The "fuse-python" package referred to is hard to locate, and is a
342 separate tarball for the python language binding distributed by the
343 fuse project on sourceforge. It is available as
344 pkgsrc/filesystems/py-fuse-bindings and on NetBSD 5, "bup fuse"
347 - "bup fuse" presents every directory/file as inode 0. The directory
348 traversal code ("fts") in NetBSD's libc will interpret this as a
349 cycle and error out, so "ls -R" and "find" will not work.
351 - There is no support for ACLs. If/when some entrprising person
352 fixes this, adjust t/compare-trees.
358 - There is no support for ACLs. If/when some enterprising person
359 fixes this, adjust t/compare-trees.
361 - In t/test.sh, two tests have been disabled. These tests check to
362 see that repeated saves produce identical trees and that an
363 intervening index doesn't change the SHA1. Apparently Cygwin has
364 some unusual behaviors with respect to access times (that probably
365 warrant further investigation). Possibly related:
366 http://cygwin.com/ml/cygwin/2007-06/msg00436.html
372 - There is no support for ACLs. If/when some enterprising person
373 fixes this, adjust t/compare-trees.
382 bup stores its data in a git-formatted repository. Unfortunately, git
383 itself doesn't actually behave very well for bup's use case (huge numbers of
384 files, files with huge sizes, retaining file permissions/ownership are
385 important), so we mostly don't use git's *code* except for a few helper
386 programs. For example, bup has its own git packfile writer written in
389 Basically, 'bup split' reads the data on stdin (or from files specified on
390 the command line), breaks it into chunks using a rolling checksum (similar to
391 rsync), and saves those chunks into a new git packfile. There is at least one
392 git packfile per backup.
394 When deciding whether to write a particular chunk into the new packfile, bup
395 first checks all the other packfiles that exist to see if they already have that
396 chunk. If they do, the chunk is skipped.
398 git packs come in two parts: the pack itself (*.pack) and the index (*.idx).
399 The index is pretty small, and contains a list of all the objects in the
400 pack. Thus, when generating a remote backup, we don't have to have a copy
401 of the packfiles from the remote server: the local end just downloads a copy
402 of the server's *index* files, and compares objects against those when
403 generating the new pack, which it sends directly to the server.
405 The "-n" option to 'bup split' and 'bup save' is the name of the backup you
406 want to create, but it's actually implemented as a git branch. So you can
407 do cute things like checkout a particular branch using git, and receive a
408 bunch of chunk files corresponding to the file you split.
410 If you use '-b' or '-t' or '-c' instead of '-n', bup split will output a
411 list of blobs, a tree containing that list of blobs, or a commit containing
412 that tree, respectively, to stdout. You can use this to construct your own
413 scripts that do something with those values.
418 'bup index' walks through your filesystem and updates a file (whose name is,
419 by default, ~/.bup/bupindex) to contain the name, attributes, and an
420 optional git SHA1 (blob id) of each file and directory.
422 'bup save' basically just runs the equivalent of 'bup split' a whole bunch
423 of times, once per file in the index, and assembles a git tree
424 that contains all the resulting objects. Among other things, that makes
425 'git diff' much more useful (compared to splitting a tarball, which is
426 essentially a big binary blob). However, since bup splits large files into
427 smaller chunks, the resulting tree structure doesn't *exactly* correspond to
428 what git itself would have stored. Also, the tree format used by 'bup save'
429 will probably change in the future to support storing file ownership, more
430 complex file permissions, and so on.
432 If a file has previously been written by 'bup save', then its git blob/tree
433 id is stored in the index. This lets 'bup save' avoid reading that file to
434 produce future incremental backups, which means it can go *very* fast unless
435 a lot of files have changed.
438 Things that are stupid for now but which we'll fix later
439 ========================================================
441 Help with any of these problems, or others, is very welcome. Join the
442 mailing list (see below) if you'd like to help.
444 - 'bup save' and 'bup restore' have immature metadata support.
446 On the plus side, they actually do have support now, but it's new,
447 and not remotely as well tested as tar/rsync/whatever's. However,
448 you have to start somewhere, and as of 0.25, we think it's ready
449 for more general use. Please let us know if you have any trouble.
451 Also, if any strip or graft-style options are specified to 'bup
452 save', then no metadata will be written for the root directory.
453 That's obviously less than ideal.
455 - bup is overly optimistic about mmap. Right now bup just assumes
456 that it can mmap as large a block as it likes, and that mmap will
457 never fail. Yeah, right... If nothing else, this has failed on
458 32-bit architectures (and 31-bit is even worse -- looking at you,
461 To fix this, we might just implement a FakeMmap[1] class that uses
462 normal file IO and handles all of the mmap methods[2] that bup
463 actually calls. Then we'd swap in one of those whenever mmap
466 This would also require implementing some of the methods needed to
467 support "[]" array access, probably at a minimum __getitem__,
468 __setitem__, and __setslice__ [3].
470 [1] http://comments.gmane.org/gmane.comp.sysutils.backup.bup/613
471 [2] http://docs.python.org/2/library/mmap.html
472 [3] http://docs.python.org/2/reference/datamodel.html#emulating-container-types
474 - 'bup index' is slower than it should be.
476 It's still rather fast: it can iterate through all the filenames on my
477 600,000 file filesystem in a few seconds. But it still needs to rewrite
478 the entire index file just to add a single filename, which is pretty
479 nasty; it should just leave the new files in a second "extra index" file
482 - bup could use inotify for *really* efficient incremental backups.
484 You could even have your system doing "continuous" backups: whenever a
485 file changes, we immediately send an image of it to the server. We could
486 give the continuous-backup process a really low CPU and I/O priority so
487 you wouldn't even know it was running.
489 - bup only has experimental support for pruning old backups.
491 While you should now be able to drop old saves and branches with
492 `bup rm`, and reclaim the space occupied by data that's no longer
493 needed by other backups with `bup gc`, these commands are
494 experimental, and should be handled with great care. See the
495 man pages for more information.
497 Unless you want to help test the new commands, one possible
498 workaround is to just start a new BUP_DIR occasionally,
499 i.e. bup-2013, bup-2014...
501 - bup has never been tested on anything but Linux, FreeBSD, NetBSD,
502 OS X, and Windows+Cygwin.
504 There's nothing that makes it *inherently* non-portable, though, so
505 that's mostly a matter of someone putting in some effort. (For a
506 "native" Windows port, the most annoying thing is the absence of ssh in
507 a default Windows installation.)
509 - bup needs better documentation.
511 According to a recent article about bup in Linux Weekly News
512 (https://lwn.net/Articles/380983/), "it's a bit short on examples and
513 a user guide would be nice." Documentation is the sort of thing that
514 will never be great unless someone from outside contributes it (since
515 the developers can never remember which parts are hard to understand).
517 - bup is "relatively speedy" and has "pretty good" compression.
519 ...according to the same LWN article. Clearly neither of those is good
520 enough. We should have awe-inspiring speed and crazy-good compression.
521 Must work on that. Writing more parts in C might help with the speed.
525 Actually, that's not stupid, but you might consider it a
526 limitation. See the ["Related Projects"](https://bup.github.io/)
527 list for some possible options.
532 bup has an extensive set of man pages. Try using 'bup help' to get
533 started, or use 'bup help SUBCOMMAND' for any bup subcommand (like split,
534 join, index, save, etc.) to get details on that command.
536 For further technical details, please see ./DESIGN.
542 bup is a work in progress and there are many ways it can still be improved.
543 If you'd like to contribute patches, ideas, or bug reports, please join the
546 You can find the mailing list archives here:
548 http://groups.google.com/group/bup-list
550 and you can subscribe by sending a message to:
552 bup-list+subscribe@googlegroups.com
554 Please see <a href="HACKING">./HACKING</a> for
555 additional information, i.e. how to submit patches (hint - no pull
556 requests), how we handle branches, etc.